Polishing method and apparatus

ABSTRACT

A polishing tool such as a fixed abrasive polishing tool or a polishing pad is used in a polishing apparatus. A workpiece is pressed against a polishing surface of the polishing tool containing a resin to bring the workpiece into sliding contact with the polishing tool, thereby polishing the workpiece. The polishing surface of the polishing tool is kept at a temperature equal to or lower than a glass transition temperature of the polishing tool.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polishing tool for use in apolishing apparatus for polishing a workpiece such as a semiconductorwafer to a flat mirror finish, and more particularly to a polishing toolsuch as a fixed abrasive polishing tool or a polishing pad and a methodof manufacturing such a polishing tool.

[0003] 2. Description of the Related Art

[0004] As semiconductor devices have become more highly integrated inrecent years, circuit interconnections have become finer and dimensionsof devices to be integrated have become smaller. From this point ofview, it may be necessary to polish and planarize a surface of asemiconductor wafer to remove a film (layer) formed on the surface ofthe semiconductor wafer. In order to planarize a surface of asemiconductor wafer, a polishing apparatus for performing chemicalmechanical polishing (CMP) has been used. This type of chemicalmechanical polishing (CMP) apparatus comprises a polishing table havinga polishing pad (polishing cloth) attached thereon, and a top ring forholding a workpiece to be polished, such as a semiconductor wafer. Theworkpiece is disposed between the polishing pad and the top ring, andpressed against the polishing pad under a certain pressure by the topring while the polishing table and the top ring are rotated. In thisstate, the workpiece is polished to a flat mirror finish while apolishing liquid (slurry) is supplied onto the polishing pad.

[0005] In a chemical mechanical polishing process which employs suchpolishing liquid (slurry), a workpiece is polished while the polishingliquid (slurry) containing a large amount of abrasive particles issupplied onto a relatively soft polishing pad. Therefore, a problem ofpattern dependence arises. Pattern dependence means that gentleirregularities are formed on a surface of a semiconductor wafer after apolishing process due to irregularities on the surface of thesemiconductor wafer that existed before the polishing process, thusmaking it difficult to planarize the surface of the semiconductor waferto a completely flat surface. Specifically, a polishing rate is higherin an area where irregularities have small pitches (a density ofirregularities is large) and is lower in an area where irregularitieshave large pitches (a density of irregularities is small). Existence ofareas of the higher polishing rate and areas of the lower polishing ratecauses gentle irregularities to be formed on the surface of thesemiconductor wafer.

[0006] In order to solve the above problems, it has been proposed topolish a semiconductor wafer with use of a fixed abrasive (grindstone).In such a process, a surface of a semiconductor wafer or the like ispolished with a fixed abrasive which comprises abrasive particles fixedby a resin as a binder. With a process utilizing a fixed abrasive whichessentially has a large hardness, it is possible to achieve aconsiderably higher level of planarity. On the other hand, with theprocess utilizing the fixed abrasive, scratches or defects tend to beproduced on a surface of a semiconductor wafer being polished. Thus, ithas been proposed in recent years to polish a semiconductor wafer with afixed abrasive at a temperature equal to or higher than the glasstransition temperature of the binder resin used in the fixed abrasive.However, when a semiconductor wafer is polished by the fixed abrasive ata temperature equal to or higher than the glass transition temperature,the binder resin is softened and tends to be attached to thesemiconductor wafer. Once the binder resin is attached to thesemiconductor wafer, the binder resin cannot easily be cleaned away.

[0007] The fixed abrasive polishing tool is typically manufactured asfollows: Abrasive particles and a resin are dispersed in a liquid, andthe dispersion is dried to form a mixed powder, and the mixed powder isthen compressed and heated to mold a fixed abrasive. If the grainboundary produced when the dispersion is dried to form the mixed powderremains after molding or forming, then the grain boundary is liable tocause scratches to be produced on the semiconductor wafer that is beingpolished by the fixed abrasive. The same phenomenon tends to occur withnot only the fixed abrasive, but also the polishing pad.

SUMMARY OF THE INVENTION

[0008] It is therefore an object of the present invention to provide apolishing apparatus and method for reducing defects such as scratches orresin deposits on a surface of a workpiece, being polished, such as asemiconductor wafer, and performing a better polishing action on variousworkpieces to be polished.

[0009] Another object is to provide a method of manufacturing apolishing tool for use in such polishing apparatus and method.

[0010] According to a first aspect of the present invention, there isprovided a polishing method for polishing a workpiece, comprising:pressing a workpiece against a polishing surface of a polishing toolcontaining a resin to bring the workpiece into sliding contact with thepolishing tool, thereby polishing the workpiece with abrasive particles;wherein at least a part of the polishing tool is kept at a temperatureequal to or lower than a glass transition temperature of the polishingtool.

[0011] According to another aspect of the present invention, there isprovided a polishing method for polishing a workpiece, comprising:pressing a workpiece against a polishing surface of a polishing toolcontaining a resin to bring the workpiece into sliding contact with thepolishing tool, thereby polishing the workpiece with abrasive particles;wherein a processing circumstance is kept at a temperature equal to orlower than a glass transition temperature of the polishing tool. Theprocessing circumstance is defined as a processing point or area(polishing surface), and a medium or a member located around theprocessing point or area. For example, in the case where the processingpoint or area is the polishing surface, the medium or the member locatedaround the processing point or area is a polishing liquid, a dressingliquid, a workpiece such as a semiconductor wafer, a dresser, or aprocessing assistance member.

[0012] According to a second aspect of the present invention, there isprovided a polishing apparatus for polishing a workpiece, comprising: apolishing tool containing a resin; a holder for holding and pressing aworkpiece against the polishing tool to bring the workpiece into slidingcontact with the polishing tool, thereby polishing the workpiece withabrasive particles; a temperature regulating device for keeping thepolishing tool at a temperature equal to or lower than a glasstransition temperature of the polishing tool.

[0013] According to the present invention, the polishing tool is used topolish the workpiece at the temperature equal to or lower than the glasstransition temperature of the polishing tool, and hence the resin usedas a binder resin is prevented from being softened. Therefore, the yieldis prevented from being lowered by resin deposits which would otherwiseoccur on the workpiece due to the softened resin.

[0014] In a preferred aspect of the present invention, the polishingsurface of the polishing tool is kept at the temperature equal to orlower than the glass transition temperature of the polishing tool.

[0015] In a preferred aspect of the present invention, a table or a baseplate on which the polishing tool is mounted is cooled to cool thepolishing tool or regulate the temperature of the polishing tool to thetemperature equal to or lower than the glass transition temperature ofthe polishing tool.

[0016] In a preferred aspect of the present invention, a polishingliquid having a temperature equal to or lower than the glass transitiontemperature of the polishing tool is supplied to the polishing surfacewhile the workpiece is being polished.

[0017] In a preferred aspect of the present invention, the polishingliquid comprises cold water or a chemical liquid.

[0018] In a preferred aspect of the present invention, a dressing liquidhaving a temperature equal to or lower than the glass transitiontemperature of the polishing tool is supplied to the polishing surfacewhile the polishing surface is being dressed.

[0019] In a preferred aspect of the present invention, a surface of theworkpiece being polished is cooled to cool the surface of the workpieceor to regulate the temperature of the surface of the workpiece, therebycooling the polishing tool or regulating the temperature of thepolishing tool to the temperature equal to or lower than the glasstransition temperature of the polishing tool.

[0020] In a preferred aspect of the present invention, the methodfurther comprises holding a processing assistance member in contact withthe polishing surface; and cooling the processing assistance member orregulating the temperature of the processing assistance member to keepthe polishing tool at the temperature equal to or lower than the glasstransition temperature of the polishing tool.

[0021] In a preferred aspect of the present invention, the processingassistance member comprises a dresser for dressing the polishing tool ora member attached to the dresser, the dresser or the member being heldin contact with the polishing tool.

[0022] In a preferred aspect of the present invention, the processingassistance member is operable independently of the dresser and a holderfor holding the workpiece, and the processing assistance member is heldin contact with the polishing tool.

[0023] In a preferred aspect of the present invention, the processingassistance member is attached to a holder for holding the workpiece andheld in contact with the polishing tool.

[0024] According to a third aspect of the present invention, there isprovided a method of manufacturing a polishing tool, comprising: dryinga mixed liquid including a resin and chemical agents to form a driedsolid material; and compressing and forming the dried solid materialwith heat into a polishing tool; wherein the drying temperature is lowerthan the temperature of the compressing and forming.

[0025] According to a fourth aspect of the present invention, there isprovided a method of manufacturing a polishing tool, comprising: dryinga mixed liquid including a resin and chemical agents to form a driedsolid material; and compressing and forming the dried solid materialwith heat into a polishing tool; wherein the temperature of thecompressing and forming is higher than a glass transition temperature ofthe resin or a dissolution temperature of the resin.

[0026] According to a fifth aspect of the present invention, there isprovided a method of manufacturing a polishing tool, comprising: dryinga mixed liquid including a resin and chemical agents to form a driedsolid material; and compressing and forming the dried solid materialwith heat into a polishing tool; wherein a resin solvent is added to themixed liquid.

[0027] According to a sixth aspect of the present invention, there isprovided a method of manufacturing a polishing tool, comprising: dryinga mixed liquid including a resin and chemical agents to form a driedsolid material; and compressing and forming the dried solid materialwith heat into a polishing tool; wherein an organic solvent or a foamingagent is added to the dried solid material.

[0028] According to the present invention, a grain boundary is preventedfrom being developed in the dried solid material when the mixed liquidis dried with heat, and is prevented from being left in the polishingtool after compressing and forming the dried solid material with heat.Consequently, a workpiece which is polished by the polishing tool isprevented from being scratched by a grain boundary which would otherwisebe developed in the polishing tool when the mixed liquid is dried intothe dried solid material.

[0029] In a preferred aspect of the present invention, the mixed liquidincludes abrasive particles.

[0030] The above and other objects, features, and advantages of thepresent invention will become apparent from the following descriptionwhen taken in conjunction with the accompanying drawings whichillustrate preferred embodiments of the present invention by way ofexample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a cross-sectional view of a polishing apparatusaccording to an embodiment of the present invention;

[0032]FIG. 2 is a cross-sectional view of a modification of thepolishing apparatus shown in FIG. 1;

[0033]FIG. 3 is a view, partly in block form, of a cooling ortemperature regulating apparatus;

[0034]FIG. 4 is a view, partly in block form, of a modification of thecooling or temperature regulating apparatus shown in FIG. 3;

[0035]FIG. 5 is a vertical cross-sectional view of a wafer carrier (topring) in the polishing apparatus according to an embodiment of thepresent invention;

[0036]FIG. 6 is a vertical cross-sectional view of a dresser in thepolishing apparatus according to an embodiment of the present invention;

[0037]FIG. 7A is a vertical cross-sectional view of a general ring-typedresser;

[0038]FIGS. 7B, 7C and 7D are vertical cross-sectional views of variousdressers which have a cooling (temperature regulating) function,respectively;

[0039]FIGS. 8A and 8B are plan views showing a contact member forregulating the temperature of a polishing tool that is providedindependently of a wafer carrier (wafer holder) and a dresser;

[0040]FIG. 8C is a vertical cross-sectional view of the contact member;

[0041]FIG. 9 is a flowchart of a method of manufacturing a polishingtool according to an embodiment of the present invention;

[0042]FIG. 10 is a schematic diagram showing an ultrasonic dispersingprocess for ultrasonically dispersing a mixed liquid;

[0043]FIG. 11 is a schematic diagram showing a process of forming agranulated powder with a spray drier;

[0044]FIGS. 12A through 12C are cross-sectional views showing a processof heating and compressing a forming material (granulated powder) toform a compact;

[0045]FIGS. 13A and 13B are perspective views of completed fixedabrasive polishing tools; and

[0046]FIGS. 14A through 14E are cross-sectional views showing the mannerin which a fixed abrasive polishing tool containing a chemical agent(water-absorbing resin) operates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] A polishing tool and a polishing apparatus incorporating thepolishing tool according to embodiments of the present invention will bedescribed below.

[0048] First, a glass transition temperature (Tg) will be describedbelow. When a thermoplastic macromolecure (linear macromolecule) isheated, the linear macromolecule starts thermal motion at a certaintemperature, thus changing into a rubber-like state in its entirety. Thecertain temperature referred to the above is defined as a glasstransition temperature. At the glass transition temperature, the linearmacromolecure changes from a hard brittle state such as a glass-likestate to a pliable state. Some resins exhibit fluidity when they areheated to a temperature equal to or higher than the glass transitiontemperature (Tg). The melting temperature (dissolution temperature) ofmacromolecule is generally referred to as a melting point (Tm). Thedissolution temperatures of macromolecules are sometimes not definite,and hence need to be distinguished from general melting temperatures.Furthermore, some resins are not melted, but are pyrolyzed or cured.Specifically, a thermoplastic resin, in particular a formed resin (aresin formed of linear macromolecule), has linear macromoleculesintertwined into a solid, like a nonwoven fabric. At temperatures belowthe glass transition temperature (Tg), the linear macromolecules remainfirmly intertwined. Even if external forces are applied to the linearmacromolecule at those temperatures, the intertwined structure may bedeformed, but is prevented from being disentangled. Therefore, thelinear macromolecule is generally highly resistant to external forces.In environments higher than the glass transition temperature (Tg), butlower than temperatures at which linear macromolecules are dissolved,melted, pyrolyzed, or cured, the intersection points where the moleculesare intertwined are liable to move.

[0049] In a polishing process in which a workpiece such as asemiconductor wafer is pressed against and brought in sliding contactwith a polishing tool composed mainly of a thermoplastic resin, therebypolishing the workpiece with abrasive particles, when the workpiece ispolished at a temperature higher than the dissolution temperature of thethermoplastic resin, the polishing tool becomes soft and is less likelyto produce scratches on the surface of the workpiece. However, thethermoplastic resin is dissolved and easily attached to the surface ofthe workpiece being polished. When the workpiece is polished at atemperature higher than the glass transition temperature, thethermoplastic resin changes from a solid state to a viscous state and iseasily attached to the surface of the workpiece being polished. If sucha thermoplastic resin is actually attached to the polished surface of asemiconductor wafer, then the thermoplastic resin deposit may bedissolved by sulfuric acid with oxygenated water added, hydrochloricacid (35% aq), or an organic solvent such as acetone or the like, or theoutermost surface of the polished wafer may be dissolved by DHF or thelike to cause the thermoplastic resin deposit to be removed away. At anyrate, a new cleaning process needs to be added, making it difficult todeal with the thermoplastic resin deposit within a short period of time.

[0050] According to the present invention, in a process in which aworkpiece such as a semiconductor wafer is pressed against and broughtin contact with a polishing tool containing a resin, thereby polishingthe workpiece with abrasive particles, the processing circumstance iskept at a temperature equal to or lower than a glass transitiontemperature (Tg) of the polishing tool.

[0051] By keeping the processing temperature at a melting point (Tm) orless, and a glass transition temperature (Tg) or less, the resin is in aglass state to prevent itself from being attached to a surface of theworkpiece being polished. Preferably, the glass transition temperature(Tg) of the resin should be equal to or higher than the ordinarytemperature for the purpose of handling the polishing tool. If the glasstransition temperature (Tg) of the resin were lower than the ordinarytemperature, the resin would tend to become soft, making it difficult tohandle the polishing tool. If an aqueous polishing liquid is used in thepolishing process, because the polishing liquid is frozen at nearly 0°C., the range of temperatures in which the polishing liquid can be usedis narrow.

[0052] The resin to be used maybe prepared by mixing or polymerizingvarious resins. The resins should have an average glass transitiontemperature (Tg) equal to or higher than the ordinary temperature, andthe polishing tool should be used during a polishing process at atemperature equal to or lower than the average glass transitiontemperature (Tg). More preferably, among resin materials or constituentresins, the glass transition temperature (Tg) of resin component havingthe lowest glass transition temperature should be equal to or higherthan the ordinary temperature, thereby effectively reducing theattachment of the resin to the surface being polished.

[0053] As a method for controlling the temperature of a polishing toolduring a polishing process, there are a method in which the temperatureof the polishing tool is regulated by cooling the reverse side of thepolishing tool or regulating the temperature of the reverse side of thepolishing tool, and a method in which the temperature of the polishingtool is regulated by cooling the polishing surface or regulating thetemperature of the polishing surface. As a method for cooling apolishing surface or regulating the temperature of a polishing surface,there are a method for applying cooling air to the polishing surface, amethod for using a polishing liquid which can be easily evaporated, amethod for utilizing evaporation heat generated when a polishing liquidis evaporated by, for example, spraying the polishing liquid, and amethod for performing a heat exchange with a member which is brought indirect contact with the polishing surface.

[0054] As a means or device for cooling a polishing tool or regulatingthe temperature of the polishing tool to a temperature equal to or lowerthan the glass transition temperature (Tg) of the polishing tool, ameans or device for cooling a table or a base plate or regulating thetemperature of the table or the base plate as shown in FIG. 1 can beemployed.

[0055] As shown in FIG. 1, in a polishing apparatus 100, a semiconductorwafer W, which is a workpiece to be polished, is pressed against andbrought in sliding contact with a polishing tool 10, and is polishedwith abrasive particles. The polishing tool 10 is mainly composed of athermoplastic resin. The polishing tool 10 is fixedly mounted on aturntable 50 through a base plate 20, and is rotatable by the turntable50 about an axis of a main shaft coupled to the turntable 50. Thesemiconductor wafer W is supported on a top ring 110 and is rotatable bythe top ring 110 about an axis of a main shaft coupled to the top ring110. The top ring 110 constitutes a wafer carrier or a wafer holder. Thesemiconductor wafer W supported on the top ring 110 is pressed againstand brought in sliding contact with the polishing surface of therotating polishing tool 10, and hence the semiconductor wafer W isprogressively polished. At this time, the polishing surface of thepolishing tool 10 is supplied with a polishing liquid containing a largeamount of abrasive particles from a nozzle 130. The polishing apparatus100 also has a dresser 120 having a dressing surface 121. The dressingsurface is pressed against and brought in sliding contact with thepolishing surface of the polishing tool 10, thereby dressing thepolishing surface. Another nozzle 123 is provided to supply a dressingliquid such as pure water or the like to the polishing surface of thepolishing tool 10.

[0056] The polishing apparatus 100 has a cooling device (pipe) 60disposed in the turntable 50 for cooling the turntable 50 and the baseplate 20. The cooling device (pipe) 60 is supplied with a circulatingcooling liquid which is regulated to a predetermined temperature. Thecooling device (pipe) 60 can cool the polishing tool 10 or regulate thetemperature of the polishing tool 10 to a temperature equal to or lowerthan the glass transition temperature (Tg) of the thermoplastic resin ofthe polishing tool 10.

[0057] It is generally known that the temperature of the polishingsurface of the polishing tool increases during a polishing process, andthat the turntable of a general CMP apparatus is often provided with awater-cooled cooling unit. However, the temperature of the cooling unitoften depends on the temperature of water which is supplied from apublic water supply system to the cooling unit. The temperature of waterwhich is supplied from the public water supply system is required to bekept in a temperature range equal to or lower than the glass transitiontemperature (Tg). If water supplied from the public water supply systemfails to sufficiently cool the turntable, then it is necessary to add acooling device for cooling the turntable so that the processingtemperature is controlled so as to be equal to or lower than the meltingtemperature (Tm) and also the glass transition temperature (Tg). In thiscase, the polishing tool is cooled or the temperature of the polishingtool is regulated from the reverse side of the polishing surface of thepolishing tool, making it possible to cool the polishing toolsufficiently. If the polishing tool comprises a fixed abrasive, then thepolishing tool which is cooled by the cooling device is sufficientlyhard in its lower layer to thus provide highly flat polishingcharacteristics. Since the resin of the polishing tool is generally oflow thermal conductivity and tends to accumulate heat easily, thepolishing tool should have a thickness of 5 mm or less in order to coolthe polishing surface thereof to a temperature equal to or lower thanthe glass transition temperature (Tg).

[0058] According to the present invention, in a process in which aworkpiece is polished with abrasive particles by being pressed againstand brought in sliding contact with a polishing tool containing a resin,the polishing tool can be kept at a temperature equal to or lower thanthe glass transition temperature (Tg) of the resin by supplying apolishing liquid, or a dressing liquid such as water (cold water) or achemical liquid having a temperature equal to or lower than the glasstransition temperature of the resin onto the polishing tool duringprocessing. There are two cases for supplying a polishing liquid, or adressing liquid. In the first case, polishing of the workpiece is notcarried out during dressing, and hence only a dressing liquid issupplied to a polishing tool. Because polishing of the workpiece is notcarried out, dressing of the polishing tool can be carried out withoutregulating the temperature of the dressing liquid. However, by supplyingthe dressing liquid which is cooled or regulated in temperature, thepolishing surface of the fixed abrasive polishing tool can be preventedfrom being degraded or deteriorated. Thereafter, only a polishing liquidis supplied to the polishing tool during polishing, and hence the resinused as a binder resin is prevented from being softened and attached tothe workpiece only by supplying the polishing liquid which is cooled orregulated in temperature. In the second case, the temperature of thepolishing liquid is regulated during polishing, and when required, thedressing liquid is supplied during polishing. In this case, thepolishing liquid and the dressing liquid are separately supplied to thepolishing surface, and hence both of the polishing liquid and thedressing liquid are required to be cooled or regulated in temperature.In order to keep the polishing surface of the polishing tool at adesired temperature, the polishing surface should preferably be cooleddirectly. Therefore, a member for directly contacting the polishingsurface may be used for performing a heat exchange with the polishingsurface during processing. The outermost surface of the polishing toolcan be controlled at a temperature equal to or lower than the glasstransition temperature (Tg) of the resin by cooling the polishing liquidor the dressing liquid, or regulating the temperature of the polishingliquid or the dressing liquid.

[0059] According to the present invention, in a process in which aworkpiece is polished with abrasive particles by being pressed againstand brought in sliding contact with a polishing tool containing a resin,in order to cool the surface of the workpiece being polished or regulatethe temperature of the surface of the workpiece being polished so thatthe workpiece is kept at a temperature equal to or lower than the glasstransition temperature (Tg) of the resin, a polishing liquid whosetemperature is controlled to a predetermined temperature is suppliedfrom a nozzle 130 to the polishing tool 10, or a dressing liquid whosetemperature is controlled to a predetermined temperature is suppliedfrom a nozzle 123 to the polishing tool 10 as shown in FIG. 2. Thus, thepolishing surface of the polishing tool 10 can be controlled at atemperature equal to or lower than the glass transition temperature (Tg)of the resin. Preferably, each of the nozzles 123, 130 is covered with aheat insulation 135 and has its tip end combined with a temperaturesensor 140, there by controlling each of the nozzles 123, 130 at apredetermined temperature. As shown in FIG. 3 or FIG. 4, the polishingliquid supplied to the nozzle 130 or the dressing liquid supplied to thenozzle 123 can be cooled, or the temperature of the polishing liquidsupplied to the nozzle 130 or the dressing liquid supplied to the nozzle123 can be regulated, by a heat exchanger.

[0060] As shown in FIG. 3, a polishing liquid or a dressing liquidstored in a supply tank 71 is delivered through a supply line 72 by apump 73 to the nozzle 130 or 123 (see FIG. 2). A container 74 isprovided to store a liquid such as water which is cooled by a coil 75 aof a heat exchanger 75. A part of the supply line 72 is cooled by theliquid stored in the container 74. Thus, the polishing liquid or thedressing liquid is cooled by the heat exchanger 75 to a predeterminedtemperature before it reaches the nozzle 130 or 123.

[0061] As shown in FIG. 4, a polishing liquid or a dressing liquidstored in a supply tank 71 is delivered through a supply line 72 by apump 73 to the nozzle 130 or 123 (see FIG. 2). A heat exchanger 76 isprovided so as to enclose a part of the supply line 72. Thus, thepolishing liquid or the dressing liquid flowing through the supply line72 is cooled by the heat exchanger 76 to a predetermined temperaturebefore it reaches the nozzle 130 or 123.

[0062]FIG. 5 shows a top ring (wafer carrier or wafer holder) 110 forholding a semiconductor wafer W. The top ring 110 has a cooling pipe(temperature regulating pipe) 150 disposed therein, and a cooling liquid(temperature regulating liquid) 152 is supplied to the cooling pipe(temperature regulating pipe) 150 through a rotary joint 151. Thepolishing tool 10 (see FIG. 1 or 2) can be cooled or the temperature ofthe polishing tool 10 can be regulated to a temperature equal to orlower than the glass transition temperature (Tg) of the polishing tool10 by the cooling liquid (temperature regulating liquid) 152 suppliedvia the cooling pipe (temperature regulating pipe) 150 through thesemiconductor wafer W which is held against the polishing surface of thepolishing tool 10. If the semiconductor wafer W is locally cooled or thetemperature of the semiconductor wafer W is locally regulated by thecooling liquid (temperature regulating liquid) 152, then thesemiconductor wafer W tends to be deformed due to difference in thermalexpansion. Therefore, the cooling pipe (temperature regulating pipe) 150should preferably be arranged in the top ring 110 so that the entiretyof the top ring 110 is cooled or the temperature of the entirety of thetop ring 110 is regulated.

[0063]FIG. 6 shows a dresser 120 combined with a cooling pipe(temperature regulating pipe) 153 for cooling the polishing surface ofthe polishing tool 10. Specifically, the cooling pipe (temperatureregulating pipe) 153 is disposed in the dresser 120 and is supplied witha cooling liquid (temperature regulating liquid) 155 through a rotaryjoint 154. When the cooling liquid (temperature regulating liquid) 155flows through the cooling pipe (temperature regulating pipe) 153, thedresser 120 is cooled or the temperature of the dresser 120 isregulated, whereby the polishing surface of the polishing tool 10 iscooled through the dressing surface 121. In this manner, the polishingsurface of the polishing tool 10 can be kept at a temperature equal toor lower than the glass transition temperature (Tg) of the polishingtool 10. In order to prevent the dresser 120 from being deformed due todifference in thermal expansion, it is preferable to provide the coolingpipe (temperature regulating pipe) 153 in the dresser 120 so as to coolthe entirety of the dresser 120 including the dressing surface 121. Thecooling liquid (temperature regulating liquid) 155 may comprise water orthe like which is cooled or regulated in temperature to a predeterminedtemperature, and supplied to the cooling pipe (temperature regulatingpipe) 153 in an amount sufficiently large for keeping the polishingsurface of the polishing tool 10 at a temperature equal to or lower thanthe glass transition temperature (Tg). The top ring 110 or the dresser120 may be provided with a temperature sensor so that the top ring 110or the dresser 120 can be controlled at a predetermined temperature.

[0064] According to the present invention, in a process in which aworkpiece is polished with abrasive particles by being pressed againstand brought in sliding contact with a polishing tool containing a resin,a processing assistance member may be used for contacting the polishingsurface of the polishing tool 10 to cool the polishing tool 10 orregulate the temperature of the polishing tool 10 to a temperature equalto or lower than the glass transition temperature (Tg) of the polishingtool during processing. The processing assistance member may comprise adresser or a member attached to the dresser and held in contact with thepolishing tool 10. For example, a polishing tool contact member disposedaround the dresser may be cooled, or may be regulated in temperature tocool the polishing tool or regulate the temperature of the polishingtool, thereby keeping the polishing tool at a temperature equal to orlower than the glass transition temperature (Tg). In this manner, thepolishing surface of the polishing tool 10 can be kept in a glass statefor thereby reducing resin deposits on the polished surface of theworkpiece. The polishing tool contact member disposed around the dresseris also effective to prevent the dresser from being tilted due to wear,thus providing uniform dressing effect of the polishing tool 10.

[0065]FIGS. 7A through 7D show various cooling members (temperatureregulating members) attached to dressers. FIG. 7A shows a generalring-type dresser, and FIGS. 7B through 7D show various dresserscombined with respective contact members for cooling the polishing toolor regulating the temperature of the polishing tool. Specifically, FIG.7A shows a dresser holder 120 with an annular dresser tool 121 mountedon a lower surface thereof. The dresser holder 120 is supported on thelower end of a main shaft 122 through a ball joint 122 a.

[0066]FIG. 7B shows a dresser with a retainer temperature regulator. Asshown in FIG. 7B, a cooling pipe (temperature regulating pipe) 125 isdisposed in a dresser holder 120 and supplied with a cooling liquid(temperature regulating liquid) 127 from a cooling liquid (temperatureregulating liquid) supply device (not shown) through a rotary joint 126.An annular retainer 128 a made of a high heat transfer material isdisposed around an annular dresser tool 121 mounted on the lower surfaceof the dresser holder 120. The cooling liquid (temperature regulatingliquid) 127 flowing through the cooling pipe (temperature regulatingpipe) 125 cools the polishing surface of the polishing tool 10 orregulates the temperature of the polishing surface of the polishing tool10 through the dresser holder 120. Therefore, the dresser shown in FIG.7B is capable of cooling the polishing surface of the polishing tool 10or regulating the temperature of the polishing surface of the polishingtool 10 while dressing the polishing tool 10 with the dresser tool 121.Because the dresser tool 121 is of a ring shape and has a small area ofcontact with the polishing tool 10, the retainer 128 a should preferablycomprise a highly flat member having a flatness of 0.1 mm or less. Thering-shaped retainer 128 a is effective to stabilize the ring-shapeddresser tool 121 in operation and also to condition the polishingsurface of the polishing tool 10 which has been excessively roughened bydressing. The surface of the retainer 128 a which is held in contactwith the polishing tool 10 may have a radial, concentric, spiral, orgrid-like pattern of grooves for draining the waste dressing liquid.

[0067]FIG. 7C shows a dresser having a dresser holder 120 combined witha heat accumulator 129. The dresser has a cooling pipe (temperatureregulating pipe) 125 disposed in the dresser holder 120 for circulatinga cooling liquid (temperature regulating liquid) 127. The heataccumulator 129 accumulates a cold heat, and hence cools the polishingsurface of the polishing tool 10 through the dresser tool 121 while thepolishing surface is being dressed by the dresser tool 121.

[0068]FIG. 7D shows a dresser with an inner circumference temperatureregulator. As shown in FIG. 7D, a contact member 128 b for cooling thepolishing tool 10 or regulating the temperature of the polishing tool 10is disposed on the lower surface of a dresser holder 120 at a positionradially inwardly of an annular dresser tool 121. The dresser tool 121is disposed on an outer circumferential region of the dresser holder120. The contact member 128 b made of a high heat transfer material isdisposed inwardly of the dresser tool 121. A cooling pipe (temperatureregulating pipe) 125 is disposed in the dresser holder 120 and suppliedwith a cooling liquid (temperature regulating liquid) 127 from a coolingliquid (temperature regulating liquid) supply device (not shown) througha rotary joint 126. Because the contact member 128 b is disposed on aninner circumferential region of the dresser holder 120 and the dressertool 121 is disposed on an outer circumferential region of the dresserholder 120, the waste dressing liquid can be easily drained from thedresser tool 121. Thus, it is not necessary to form a complex pattern ofgrooves in the surface of the contact member 128 b which is held againstthe polishing surface of the polishing tool 10.

[0069] Each of the dressers shown in FIGS. 7A through 7D shouldpreferably be combined with a temperature sensor for feedback of thetemperature of the cooling liquid (temperature regulating liquid) to thecooling liquid (temperature regulating liquid) supply device for therebycontrolling the temperature of the cooling liquid (temperatureregulating liquid) accurately. The temperature sensor may comprise aradiation thermometer, a thermocouple, a resistance temperature sensor,a thermistor, or the like. The temperature sensor may be positionedwithin the contact member such as a retainer or on the dresser holder.

[0070] A processing assistance member for contacting the polishing toolto cool the polishing tool or regulate the temperature of the polishingtool may be provided independently of a dresser holder having a dressertool or a top ring for holding a semiconductor wafer. For example, apolishing tool contact member which can be controlled in operationindependently of the dresser and the wafer carrier (wafer holder) may beprovided for cooling the polishing tool or regulating the temperature ofthe polishing tool to keep the polishing surface of the polishing toolat a temperature equal to or higher than the glass transitiontemperature of the polishing tool. Because the resin of the polishingtool is in a glass state during a polishing process, resin deposits onthe polishing surface of the semiconductor wafer can be reduced. Thepolishing tool contact member which can be controlled in operationindependently of the dresser and the wafer carrier (wafer holder) cancondition the polishing surface of the polishing tool by controlling thecontact pressure applied by the polishing tool contact member, thusperforming stable dressing. Then, stable polishing of the semiconductorwafer can be performed using the stably dressed polishing tool. Theindependent polishing tool contact member may be fixed in position ormay be angularly moved. The pressure applied by the polishing toolcontact member, the angular movement of the polishing tool contactmember, and the position fixing of the polishing tool contact member maybe controlled to control the amount of material removed from thepolishing tool while the polishing tool is being monitored. If thepolished configuration of the semiconductor wafer can be predicted, thenthe pressure applied by the polishing tool contact member, the angularmovement of the polishing tool contact member, and the position fixingof the polishing tool contact member can be selected based on apredicted value.

[0071]FIGS. 8A through 8C show polishing apparatuses having anindependent contact member that can be operated independently of adresser and a top ring.

[0072]FIG. 8A shows a stationary-type polishing apparatus comprising atop ring 110 for holding a semiconductor wafer W and a dresser 120 fordressing a rotatable polishing tool 10, the top ring 110 and the dresser120 being fixedly positioned with respect to the polishing tool 10 andbeing rotatable about their own axes, respectively. The polishingapparatus also has an independent contact member 160 for cooling thepolishing tool 10 or regulating the temperature of the polishing tool 10independently of the top ring 110 and the dresser 120. As shown in FIG.8C, a cooling pipe (temperature regulating pipe) 164 is disposed in aholder 161, and a cooling liquid (temperature regulating liquid) 165 issupplied from a cooling liquid (temperature regulating liquid) supplydevice (not shown) to the cooling pipe (temperature regulating pipe) 164through a main shaft 162 and a rotary joint 163, thereby cooling theentire contact member 160 or regulating the temperature of the entirecontact member 160. The contact member 160 is made of a high heattransfer material for transferring a cold heat supplied from the coolingpipe (temperature regulating pipe) 164 to the polishing tool 10, therebycooling the polishing surface of the polishing tool 10 or regulating thetemperature of the polishing surface of the polishing tool 10. Thus, thepolishing surface of the polishing tool 10 is kept at a temperatureequal to or lower than the glass transition temperature, and hence theresin of the polishing tool 10 is in a glass state, thus reducing resindeposits on the polished surface of the semiconductor wafer W.

[0073]FIG. 8B shows a swingable-type polishing apparatus comprising atop ring 110 supported on a swing arm 110 a, a dresser 120 supported ona swing arm 120 a, and an independent contact member 160 supported on aswing arm 160 a. The swing arms 110 a, 120 a and 160 a are swingable,when necessary, with respect to a polishing tool 10. When the swing arm110 a is swung, the top ring 110 is angularly moved with respect to thepolishing tool 10 for increasing an area of contact of the semiconductorwafer W with the polishing tool 10. When the swing arm 120 a is swung,the dresser 120 is angularly moved with respect to the polishing tool 10for dressing an increased area of the polishing tool 10. When the swingarm 160 a is swung, the independent contact member 160 is angularlymoved with respect to the polishing tool 10 for preferentiallyregulating the temperature of a region of the polishing tool 10 which ismore likely to change than that of other regions thereof.

[0074] A member for directly contacting the polishing tool may comprisea member attached to the wafer carrier (wafer holder) and held incontact with the polishing tool. For example, a polishing tool contactmember such as a retainer ring disposed around the top ring may becooled, or the temperature of the polishing tool contact member may beregulated to cool the polishing tool or regulate the temperature of thepolishing tool.

[0075] Materials which can be used to make up the polishing tool will bedescribed in detail below.

[0076] Generally, a polishing tool is made up of a resin, pores, whenrequired, abrasive particles, and chemical agents. The resin shouldpreferably comprise a thermoplastic resin rather than a thermosettingresin. If the polishing tool is a fixed abrasive polishing tool, itcontains abrasive particles. Materials for abrasive particles maycomprise cerium oxide (CeO₂), titanium oxide (TiO₂: though titaniumoxide is available in rutile and anatase crystalline structures, anatasetitanium oxide is preferable as it is more reactive), alumina (Al₂O₃),silicon carbide (SiC), silicon oxide (SiO₂), zirconia (ZrO₂), iron oxide(FeO, Fe₃O₄), manganese oxide (MnO₂, Mn₂O₃), magnesium oxide (MgO),calcium oxide (CaO), barium oxide (BaO), zinc oxide (ZnO), bariumcarbonate (BaCO₃), calcium carbonate (CaCO₃), diamond (C), or acomposite material thereof. The materials for abrasive particles may bein the form of a powder or a slurry. However, in order to produce auniform fixed abrasive, it is preferable to use slurry-like abrasiveparticles in which fine abrasive particles are stably present. Morepreferably, the polishing tool should contain abrasive particles havinga particle diameter of from 10 nm to 10 μm. Further, in order to producea polishing tool for processing semiconductor wafers, any metalscontained in materials for abrasive particles should be minimized.

[0077] Thermosetting resins that can be used in the polishing toolinclude phenol-formaldehyde resin (PF), urea-formaldehyde resin (UF),melamine-formaldehyde resin (MF), unsaturated polyester resin (UP),epoxy resin (EP), silicone (SI), polyurethane (PUR), etc.

[0078] Thermoplastic resins that can be used in the polishing toolinclude polyvinyl chloride (PVC) known as general-purpose plastics,polyethylene (PE), polypropylene (PP), polystyrene (PS),acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene (AS),polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylidenechloride (PVDC), polyethylene terephthalate (PET), polyamide (PA) knownas general-purpose engineering plastics, polyacetal (POM), polycarbonate(PC), polyphenylene ether (PPE) (modified PPO), polybutyleneterephthalate (PBT), ultra-high-molecular-weight polyethylene (UHMWPE),polyvinylidene fluoride (PVDF), polysulfone (PSF) known as superengineering plastics, polyethersulfone (PES), polyphenylene sulfide(PPS), polyarylate (PAR), polyamideimide (PAI), polyehterimide (PEI),polyether ether ketone (PEEK), polyimide (PI), andpolytetrafluoroethylene (PTFE). Of these resins, ABS and PVDF areparticularly effective for removing scratches. Two or more of the aboveresins may be mixed with each other for use in the polishing tool.Monomers of the above resins may be copolymerized.

[0079] If the polishing tool needs to be a soft polishing tool, thenpreferred resins for use in such soft polishing tool include polyvinylfluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, vinylfluoride, vinylidene fluoride, dichlorofluoroethylene, vinyl chloride,vinylidene chloride, perfluoro-α-olefins (for example,hexafluoropropylene, perfluorobutene-1, perfluoropentene-1,perfluorohexene-1, or the like), perfluorobutadiene,chlorotrifluoroethylene, trichloroethylene, tetrafluoroethylene,perfluoroalkyl perfluorovinyl ethers (for example, perfluoromethylperfluorovinyl ether, perfluoroethyl perfluorovinyl ether,perfluoropropyl perfluorovinyl ether, or the like), alkyl vinyl etherwith the number of carbon atoms ranging from 1 to 6, allyl vinyl etherwith the number of carbon atoms ranging from 6 to 8, alkyl with thenumber of carbon atoms ranging from 1 to 6, allyl perfluorovinyl ether,ethylene, propylene, styrene, or the like with the number of carbonatoms ranging from 6 to 8, polyvinylidene fluoride, polyvinyl fluoride,vinylidene fluoride-tetrafluoroethylene copolymer, vinylidenefluoride-hexafluoropropylene copolymer, tetrafluoroethylene-ethylenecopolymer, tetrafluoroethylene-propylene copolymer,ethylene-chlorotrifluoroethylene copolymer,tetrafluoroethylene-chlorotrifluoroethylene copolymer,tetrafluoroethylene-hexafluoropropylene copolymer,tetrafluoroethylene-perfluoromethyl perfluorovinyl ether copolymer,tetrafluoroethylene-perfluoroethyl perfluorovinyl ether copolymer,tetrafluoroethylene-perfluoropropyl perfluorovinyl ether copolymer,tetrafluoroethylene-hexafluoropropylene-perfluoromethyl perfluorovinylether copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroethylperfluorovinyl ether copolymer,tetrafluoroethylene-hexafluoropropylene-perfluoro propyl perfluorovinylether copolymer, etc.

[0080] Of the above resins, from the standpoints of foaming properties,economy, and availability, preferable resins are polyvinylidenefluoride, polychlorotrifluoroethylene, vinylidenefluoride-hexafluoropropylene copolymer, ethylene-tetrafluoroethylenecopolymer, ethylene-chlorotrifluoroethylene copolymer,tetrafluoroethylene-perfluoroalkyl perfluorovinylether copolymers, andtetrafluoroethylene-hexafluoropropylene copolymer. More preferable arepolyvinylidene fluoride and vinylidene fluoride-hexafluoropropylenecopolymer as partially fluorocarbon resins, andtetrafluoroethylene-perfluoroalkyl perfluorovinylether copolymers asperfluororesins.

[0081] It is preferable to select thermoplastic resins, and the resinsshould preferably have glass transition temperatures (Tg) equal to orhigher than the ordinary temperature.

[0082] The polymeric material may be in the form of either a powder or aliquid. In order to uniformize the composition ratio of a granulatedpowder as a forming material and increase the uniformity of the fixedabrasive, it is preferable to use a latex suspension where the polymericmaterial is uniformly dispersed in a liquid. For use in semiconductorapplications, i.e., for polishing semiconductor wafers with reducedmetal contamination, the amount of any metals contained in the polymericmaterial should be as small as possible. The thermoplastic material isgenerally manufactured by polymerizing many monomers through differentprocessing stages including addition polymerization, copolymerization,condensation polymerization, addition condensation, etc. In thoseprocessing stages, water and various agents including polymerizationcatalysts represented by organometallic compounds and inorgannometalliccompounds, polymerization-retarders, dispersing agents, activators,solvents, catalyst deactivators, stabilizers, emulsifiers, antioxidants,etc are used. The monomers are processed into the polymeric materialthrough a complex process. In order to reduce the amount of metalsintroduced into the polymeric material of the polishing tool, it ispreferable to reduce the metal compounds contained in the chemicalagents and water used in the above various polymerization stages. Thewater and solvents that are used in the polymerization process shouldpreferably comprise pure water or ultrapure water and highly puresolvents, respectively.

[0083] Other suitable additives (agents) may be added other than thepolymeric material. These additives (agents) include accelerators (forexample, amine) including micro (nano) capsule agents, stabilizers(buffers), mirror-finish improvers (water-soluble macromolecures),polishing additives such as abrasive particle anticoagulants (organicmacromolecures), abrasive particle self-sharpening regulators (binderdissolvers), fixed abrasive forming additives, fixed abrasive processingadditives (photosensitizers), etc. The amount of metals contained inthese additives should also be as small as possible.

[0084] A process of manufacturing a fixed abrasive will be describedbelow.

[0085] First, a fixed abrasive material powder is manufactured by mixingfine abrasive particles, a polymeric material, and additives including adispersing agent such as a surface active agent, a stabilizer such as abuffer, an accelerator represented by a pH adjuster such as KOH, amirror-finish improver such as a macromolecure agent, etc. The abovematerials are mixed with each other, and, if necessary, pure water and asolvent are added to the mixture. The materials are sufficientlydispersed using a stirrer, an ultrasonic dispersing device, or the like.

[0086] Then, the mixed liquid is dried by a dryer such as a spray drierinto a powder (granulated powder) in which various materials areuniformly mixed. The powder (granulated powder) has a diameter of 0.1 μmto several hundreds μm, preferably an average diameter of several μm toseveral tens μm. Alternatively, a powder may be produced byfreeze-drying and then pulverizing, coagulating, and/or precipitating.In the above powder (granulated powder) producing process, the materialsmay be mixed and then dried, or dried and then mixed, or repeatedlymixed and dried. Depending on the material to be mixed, a material maybe directly mixed with a dried powder of other materials.

[0087] Next, suitable additives (the above agents) are added to themixed powder (granulated powder) obtained by the above process, thusproducing a powdery mixture. The powdery mixture is then compressed by acompression forming machine which typically comprises a hot press,thereby producing a fixed abrasive polishing tool. The size of thecompression forming machine is determined by the size of the fixedabrasive polishing tool to be produced. Therefore, the size of thecompression forming machine may be smaller if the fixed abrasivepolishing tool is of a split type, i.e., segment type, than if the fixedabrasive polishing tool is of a non-split type. If a split-type, i.e.,segment-type fixed abrasive polishing tool is produced, then associatedfabrication equipment and subsequent processing equipment may also besmaller in size. Consequently, initial investments are smaller, and themanufacturing cost is lower.

[0088] In order to facilitate the protection of the fixed abrasive andthe installation thereof onto a polishing apparatus, the produced fixedabrasive is fixed to a member (base) having mechanical strength, such asa member made of metal or engineering plastics, by adhesion ordeposition. If the fixed abrasive is made up of a number of segmentshaving a complex shape, then the segments are difficult to be positionedwhen secured to the base. If the segments are positioned inaccurately onthe base, then the adhesive applied to secure the fixed abrasive to thebase tends to be squeezed into gaps between the segments. If theadhesive is positioned on the polishing surface of the fixed abrasive,then the adhesive is likely to hamper the polishing action or producesscratches on the semiconductor wafer being polished. Therefore, thesegments of the fixed abrasive need to be positioned accurately.

[0089] Undue gaps between the segments pose a problem in that when thesemiconductor wafer is polished by the fixed abrasive polishing tool,the area of contact between the polishing tool and the semiconductorwafer tends to vary. Because it is difficult to instantaneously changethe pressure applied to the semiconductor wafer at the time that thesemiconductor wafer is polished, a change in the area of contact betweenthe polishing tool and the semiconductor wafer causes a change in thepressure applied to the semiconductor wafer, failing to keep the amountof material removed from the semiconductor wafer stably. When thesemiconductor wafer is positioned across gaps between the segments uponrelative movement of the semiconductor wafer and the polishing tool, alarge force is imposed on the semiconductor wafer, tending to polish thesemiconductor wafer to an excessively large amount on the edge portionthereof or to produce scratches on the surface of the semiconductorwafer. In order to solve the above drawbacks, the segments of the fixedabrasive are of cyclotomic shapes or sectorial shapes with gapscontrolled therebetween, so that the segments can be positionedaccurately with relative ease and the fixed abrasive can polish thesemiconductor wafer stably. The segment-shaped fixed abrasive is alsoadvantageous in that there is no need for handling a large-sized fixedabrasive which would tend to be damaged when manufactured, and thedanger of inclusion of air bubbles into the adhesive layer used to bondthe fixed abrasive to the base is comparatively small. The inclusion ofair bubbles into the adhesive layer produces a non-bonded area in thelayer below the polishing surface to cause the fixed abrasive to beinsufficiently fixed to the base. If the fixed abrasive is notsufficiently bonded to the base, then the polishing tool may possibly beseparated from the base under frictional forces developed between thepolishing tool and the semiconductor wafer being polished, causingdamage to the fixed abrasive.

[0090] The base, which is of a circular or cylindrical shape, is made ofan aluminum alloy or engineering plastics, if the fixed abrasive has asize up to a diameter of about 600 mm. The fixed abrasive assembly thusconstructed is sufficiently strong and has a weight that can easily behandled. Generally, a rotatable thick fixed abrasive for use as apolishing tool for polishing 8-inch semiconductor wafers can bemanufactured by the above manufacturing process.

[0091] A fixed abrasive for use as a polishing tool for polishing12-inch semiconductor wafers or larger semiconductor wafers is requiredto be a size equal to or greater than a diameter of about 700 mm. Anassembly including an integrated-type fixed abrasive and base is heavyand cannot easily be handled. If such fixed abrasive assembly is of asplit-type structure made up of segments each comprising a base segmentand a fixed abrasive segment, then the segments can individually behandled with ease, and a clean room space which is required forreplacing the fixed abrasive assembly may be relatively small. Forexample, cyclotomic or sectorial segments of the fixed abrasive maybefixed to respective segments of the base which are cyclotomic orsectorial in shape except for their attachment areas, and they may beassembled together into a circular or cylindrical assembly on thepolishing apparatus. These segments can easily be handled within a cleanroom without the need for any special apparatus such as a crane, alifter, or the like.

[0092] The various processes for manufacturing the fixed abrasive, e.g.,a process of preparing materials, including mixing and dispersing stepsof the materials, a granulating process, a forming process, a mountingprocess of the fixed abrasive on a jig for attachment to the polishingapparatus, and a bonding process of the fixed abrasive to the base, maybe carried out in a clean environment, such as a clean room or a cleanbooth, which is supplied with clean air through a filter. The fixedabrasive thus manufactured is highly clean.

[0093] A process of manufacturing the polishing tool according to thepresent invention, with attention given to temperatures in themanufacturing steps, will be described below.

[0094] In a process of manufacturing a polishing tool which is composedmainly of a resin and is operable to polish a workpiece with abrasiveparticles by causing the workpiece to be pressed against and brought insliding contact with the polishing tool, a mixed liquid prepared bymixing a resin, chemical agents, and, if necessary, a slurry, issubjected to a heat treatment, and then a compression molding(compression forming) with heat, thus producing a polishing tool. Inthis case, the drying temperature of the mixed liquid is lower than theforming temperature (molding temperature) of the polishing tool. Asdescribed above, the fixed abrasive is produced by partly or fullydrying a liquid in which a slurry, a resin, polishing additives, andforming additives are mixed and dispersed, and pressing the resultantsolid material (granulated powder) with heat using a compression formingmachine which typically comprises a hot press.

[0095] The heat treatment temperature at which the mixed liquid composedof the slurry, the resin, the polishing additives, the formingadditives, and the processing additives is dried serves as a parameterwhich greatly affects the polishing tool. If the heat treatmenttemperature of the mixed liquid is higher than the forming temperatureof the polishing tool, then the interfacial bonding between the solidmaterial particles is weak, leaving interfacial defects in the formedresin. Thus, the formed resin tends to have its interfacial bondingbroken. When the interfacial bonding is broken, the abrasive particlesare liable to produce large particles during a polishing process, andthe large particles are likely to produce scratches on the surface ofthe workpiece. In order to eliminate the above shortcoming, the heattreatment temperature of the mixed liquid is made lower than the formingtemperature of the dried solid material. With the above temperaturesetting, the dried solid material can be pressed to shape in thecompression forming process at a temperature which is high enough toprevent any interfacial defects from being developed. The fixed abrasivethus formed does not produce large particles during a polishing process,and is prevented from producing large fragments which would bedetrimental to the polishing action, thereby preventing scratches frombeing produced on the workpiece being polished.

[0096] In a process of a heat treatment of a mixed liquid composed of aresin, chemical agents, and, if necessary, a slurry, and a compressionforming of a dried material to form a polishing tool, the formingtemperature of the dried material should preferably be higher than theglass transition temperature of the resin or the dissolution temperatureof the resin.

[0097] The heat treatment is carried out in the forming process at atemperature equal to or higher than the glass transition temperature(Tg) or the resin dissolving temperature (Tm) to dissolve the resin,thereby bonding the material particles together. In this manner, in theformed resin, the material particles are prevented from being separated.Since no material interfaces are left in the formed resin, but uniformbonding forces are achieved in the formed resin, the abrasive particlesare prevented from producing separate material particles or separatematerial fragments during a polishing process. Consequently, theabrasive particles are prevented from producing large fragments whichwould be detrimental to the polishing action, thereby preventingscratches from being formed on the workpiece being polished.

[0098] In a process of a heat treatment of a mixed liquid composed of aresin, chemical agents, and, if necessary, a slurry, and a compressionforming of a dried material, a resin solvent should preferably be addedto the mixed liquid at the time of the heat treatment of the mixedliquid.

[0099] By adding a resin solvent at the time of producing the formingmaterial, the solvent acts on the resin to give the resin uniformbonding forces in the forming powder material. If the forming materialis produced by a drying process typically using a spray drier, then heatis applied differently within and outside of the forming materialparticles, resulting in different bonding levels for the resin. However,the added resin solvent dissolves the resin to allow the resin to beuniformly dispersed, thus producing uniform bonding forces for theresin. The added resin solvent also acts to allow the heat treatment ofthe mixed liquid to be carried out at a lower temperature.

[0100] Rather than the heat treatment of the mixed liquid and then thecompression forming, the mixed liquid can simultaneously be dried andformed to shape according to a casting process.

[0101] In a process of a heat treatment of a mixed liquid composed of aresin, chemical agents, and, if necessary, a slurry, and a compressionforming of a dried material, it is preferable to add an organic solventor a foaming agent to the compression forming material.

[0102] The formed polishing tool has material particles which tend to beseparated due to the organic solvent or the foaming agent added to thecompression forming material. By allowing a resin solvent added to acton the forming material in the compression forming process, the formedresin has no dry powder interfaces, thus producing uniform bondingforces in the polishing tool. The resin solvent may be added not only asa liquid but also as microcapsules. With the heat, the pressure, or thefriction between the powder particles at the time of the compressionforming, the solvent in the microcapsules is released to act on theforming material. If the solvent is partly left in the formed polishingtool, then the remaining solvent provides a sterilizing effect.

[0103] The polymeric material may be in the form of either a powder or aliquid. In order to uniformize the composition ratio of a granulatedpowder as a forming material and increase the uniformity of the fixedabrasive, it is preferable to use a latex suspension where the polymericmaterial is uniformly dispersed in a liquid. For use in semiconductorapplications, i.e., for polishing semiconductor wafers with reducedmetal contamination, the amount of any metals contained in the polymericmaterial should be as small as possible. The thermoplastic material isgenerally manufactured by polymerizing many monomers through differentprocessing stages including addition polymerization, copolymerization,condensation polymerization, addition condensation, etc. In thoseprocessing stages, water and various agents including polymerizationcatalysts represented by organometallic compounds and inorgannometalliccompounds, polymerization-retarders, dispersing agents, activators,solvents, catalyst deactivators, stabilizers, emulsifiers, antioxidants,etc are used. The monomers are processed into the polymeric materialthrough a complex process. In order to reduce the amount of metalsintroduced into the polymeric material of the polishing tool, it ispreferable to reduce the metal compounds contained in the chemicalagents and water used in the above various polymerization stages. Thewater and solvents that are used in the polymerization process shouldpreferably comprise pure water or ultrapure water and highly puresolvents, respectively.

[0104] Other suitable additives (agents) may be added other than thepolymeric material. These additives (agents) include accelerators (KOH,amine, pH adjustors, or the like) including micro (nano) capsule agents,dispersant of abrasive particles such as surface active agent,stabilizers (buffers), mirror-finish improvers (water-solublemacromolecures), polishing additives such as abrasive particleanticoagulants (organic macromolecures), abrasive pariticleself-sharpening regulators (resin solvents), fixed abrasive formingadditives, fixed abrasive processing additives (photosensitizers), etc.The amount of metals contained in these additives should also be assmall as possible.

[0105] The resin solvent may differ from resin to resin to be used.General resins are easily eroded by sulfuric acid, hydrochloric acid 35%aq, an acid, an alkaline solution, or an organic solvent. For example,in the case of acrylic resins, most organic resins can be used as theresin solvent and, in particular, alcohols and ketones can easily beused as the resin solvent.

[0106] A process of manufacturing a fixed abrasive will be describedbelow with reference to FIGS. 9 through 13A and 13B.

[0107]FIG. 9 is a flow chart of a method of manufacturing a polishingtool according to an embodiment of the present invention. In FIG. 9, amanufacturing process of the polishing tool is illustrated in asimplified manner. As shown in FIG. 9, a material of a fixed abrasive isprepared in step 1, and then a forming material is produced in step 2.The forming material is compressed or heat-pressed to produce a formedbody (formed resin) in step 3, and then the formed body (formed resin)is fixed to a supporting member in step 4, thus completing a polishingtool in step 5.

[0108] Next, a manufacturing process of the fixed abrasive will bedescribed in a concrete manner in detail.

[0109] First, a fixed abrasive material powder is manufactured by mixingfine abrasive particles, a polymeric material, and additives. The abovematerials are mixed with each other, and, if necessary, pure water and asolvent are added to the mixture, thus producing a mixed liquid. Thematerials are sufficiently dispersed using a stirrer, an ultrasonicdispersing device, or the like. Specifically, a mixed liquid of anabrasive particle powder (or a slurry containing abrasive particles), aresin (a liquid resin, a resin component monomer), and various chemicalagents is ultrasonically processed, stirred, and, when necessary, issubjected to various polymerization processes, thereby sufficientlydispersing the above constituents.

[0110]FIG. 10 shows an ultrasonic dispersing apparatus forultrasonically dispersing a mixed liquid. As shown in FIG. 10, a mixedliquid accommodated in a tank 201 is stirred by a stirrer 202, anddelivered by a pump 203 to an ultrasonic dispersing apparatus 205. Theultrasonic dispersing apparatus 205 includes a hard glass flask 206 forstoring the mixed liquid supplied from the pump 203, and a container 207which is ultrasonically vibrated by an ultrasonic wave generator 208energized by a power supply 209. The container 207 stores pure water fortransmitting ultrasonic vibrations generated by the ultrasonic wavegenerator 208 to the flask 206. The mixed liquid in the flask 206 isultrasonically vibrated, and then delivered by a pump 210 through athree-way valve 213 to a tank 211. The mixed liquid is stored in thetank 211 after it has been ultrasonically dispersed. In the embodimentshown in FIG. 10, the tank 211 also has a stirrer 212 for stirring themixed liquid. However, the mixed liquid may be stirred by the stirrer202 only before the mixed liquid is ultrasonically dispersed. Though twopumps 203, 210 are shown in FIG. 10, only one pump may be employed. Themixed liquid which has been ultrasonically dispersed may be directlydelivered to a line of a next process without being stored in the tank211, so that the mixed liquid can be processed in the next process whileit is being well dispersed. Each of the pumps 203, 210 used shouldpreferably comprise a tube pump which employs a Teflon (registeredtrademark) tube for the purpose of contamination control. Similarly, thethree-way valve 213 should preferably be made of Teflon (registeredtrademark).

[0111] Then, the mixed liquid is dried by a dryer such as a spray drierinto a powder (granulated powder) in which various materials areuniformly mixed. The powder (granulated powder) has a diameter of 0.1 μmto several hundreds μm, preferably an average diameter of about severalμm. Alternatively, a mixed powder may be produced by freeze-drying andthen pulverizing, coagulating, and/or precipitating. In the above powder(granulated powder) producing process, the materials may be mixed andthen dried, or dried and then mixed, or repeatedly mixed and dried.Depending on the material to be mixed, a material may be directly mixedwith a dried powder of other materials.

[0112]FIG. 11 shows a process of forming a granulated powder using aspray drier. As shown in FIG. 11, a mixed liquid is stored in a slurrytank 251 (211) having a stirrer and is delivered by a constant-ratesupply pump 252 to an atomizer 253. The atomizer 253 sprays the mixedliquid into a container 254. The container 254 is supplied with airwhich is delivered from a hot air blower 255, heated by an electricheater or a steam heater 256, and filtered by a hot-air filter 257. Themixed liquid is atomized into a mist by the atomizer 253, and the mistis dried into-fine particles (granulated into dry particles) by the hotair in the container 254. The produced particles are delivereddownwardly to a lower portion of the container 254 where largerparticles are trapped by a collecting container 258 connected to thelower portion of the container 254. The remaining particles are carriedby air from the container 254 to a centrifugal separator 259 such as acyclone. In the centrifugal separator 259, the particles are classified,and then trapped and withdrawn from a lower portion of the centrifugalseparator 259. The air containing fine particles discharged from thecentrifugal separator 259 is supplied to a bag filter 260, where fineparticles which have not been removed by the centrifugal separator 259are removed to make the air clean. Then, the clean air is dischargedthrough an exhaust fan 261 to the atmosphere. The amount of air drawn bythe hot air blower 255 and the amount of air drawn by the exhaust fan261 are regulated so that the pressure of the interior of the container254 can be slightly negative pressure. Therefore, the particles trappedby the collecting container 258 are prevented from being scattered, orhot air is prevented from leaking from the connecting portions of thepipes. Further, sphericity of the dried powder can be increased. Thus,the drying operation can be stably performed.

[0113] The material powder thus produced may further be classified by aclassifier, if necessary.

[0114] Next, when necessary, a resin solvent and chemical agent areadded to the mixed powder (granulated powder), thus producing a formingmaterial. The forming material is then compressed and heated by acompression forming machine which typically comprises a hot press,thereby producing a fixed abrasive polishing tool. This compressionforming may be a heating and compression treatment, a compressiontreatment, or a casting forming.

[0115] A process of heating and compression forming will be describedbelow with reference to FIGS. 12A through 12C. As shown in FIG. 12A,after a lower punch 221 and a die 222 are combined with each other, aforming material powder (a granulated powder dried from a mixed liquid)223 is placed in the die 222 so as to uniformly fill up the die 222. Atthis time, a solvent may be added to the forming material powder 223,and a mixture of the forming material powder 223 and the solvent may besufficiently kneaded and then placed in the die 222. The granulatedpowder may be mixed with microcapsules 224 containing a solvent therein.Then, as shown in FIG. 12B, an upper punch 225 is placed on the formingmaterial powder so as not to impose a load to the forming materialpowder 223, and the forming material powder 223 is heated to apredetermined temperature which is equal to or higher than the softeningtemperature of the resin. Thereafter, as shown in FIG. 12C, a load isapplied to the upper punch 225 to compress the forming material powder223 into a predetermined volume. At this time, the upper punch 225 maybe pressed under positional control. Alternatively, a stopper 226 may beused to allow the upper punch 225 to compress the forming materialpowder 223 into a predetermined volume. The forming material powder 223is now compressed into a formed body (formed resin) 223 a as a polishingtool.

[0116] The die 222 may be vertically movable, and a spacer may be presetbeneath the die 222. While the forming material powder 223 is beingcompressed into the formed body (formed resin) 223 a, the spacer may beremoved to reduce residual stresses in the compressed formed body 223 a.After elapse of a predetermined period of time, the compressed formedbody 223 a is cooled, and then removed as a polishing tool from thepunches and the die.

[0117] In the case where the microcapsules 224 containing a solventtherein are used, when the forming material powder 223 is compressed andheated, the outer walls of the microcapsules 224 are broken, allowingthe solvent to flow out and act on the particle interfaces of thematerial powder. The supply of the solvent from the microcapsules 224may be controlled by a process based on time, temperature, and pressure.

[0118] In the process of manufacturing the polishing tool according tothe present invention, the drying temperature of the mixed liquid islower than the temperature of the compression forming of the formingmaterial. Thus, the generation of large particles which are responsiblefor scratches formed on the workpiece during a polishing process can besuppressed. The temperature of the compression forming is higher thanthe glass transition temperature of the resin or the dissolutiontemperature of the resin. Thus, the material particles of the formedbody are prevented from being separated from each other, and thepolishing tool having uniform bonding forces can be produced. A resinsolvent may be added to the mixed liquid at the time of heat treatment,and an organic solvent or a foaming agent may be added to the formingmaterial before the compression forming.

[0119] The formed body (formed resin) is then fixed to a support (baseplate) such as a metal plate or a plastic plate by adhesion, fusion,cohesion, or the like, thus completing a polishing tool.

[0120] After the formed resin is produced, the shape and surface of theformed resin is worked or finished, thus producing a polishing tool.Because the formed resin is generally not sufficiently strong, and tendsto crack or be broken when it is transported or fixed to a machinealone, the formed resin is fastened to a base plate. Though the formedresin may be fixed to the base plate by adhesion, fusion, cohesion, orthe like while the forming material is being compressed to shape withheat, it is preferable to fix the formed resin to the base plate afterit is compressed to shape with heat if the coefficients of thermalexpansion of the formed resin and the base plate are different from eachother or the formed resin suffers a material deterioration. This isbecause if the coefficients of thermal expansion of the formed resin andthe base plate are different from each other, the formed resin tends tobe deformed or warped when the formed resin is cooled to a temperatureat which the polishing tool is used after the formed resin has beenfixed to the base plate at a higher temperature. If the polishing toolis a fixed abrasive polishing tool including abrasive particles, thenthe formed resin should preferably be thicker for a longer service life.However, if the polishing tool comprises a fixed abrasive which wears alittle when it is in use, then the polishing tool may be in the form ofa thin flat plate. At any rate, if the fixed abrasive polishing tool isused while water or a liquid is being supplied thereto, then the fixedabrasive tends to swell, and hence the fixed abrasive should preferablybe fixed to the base plate in such a state that the fixed abrasive isactually used. Specifically, if a liquid seeps into the fixed abrasivewhen the fixed abrasive is in use, then the fixed abrasive swells, andhence the fixed abrasive should be kept in a swollen state in advanceand then fixed to the base plate. Thereafter, the fixed abrasive shouldbe kept in that state until it is used.

[0121]FIGS. 13A and 13B show completed fixed abrasive polishing tools,respectively. FIG. 13A illustrates a polishing tool having a formed body(formed resin) 25 serving as a fixed abrasive or a polishing pad andfixed to a base plate 26. FIG. 13B illustrates a split-type polishingtool composed of a plurality of segments. As shown in FIG. 13B, thesplit-type polishing tool has a fixed abrasive 25 as a formed resinwhich is composed of a plurality of separable members 25 a, 25 b, . . ., 25 f. Each of the separable members 25 a, 25 b, . . . , 25 f is in theshape of a sectorial segment. These segmental separable members 25 a, 25b, . . . , 25 f are fixed to a base plate 26 by adhesion or the like toprovide a uniform polishing surface.

[0122]FIGS. 14A through 14E show the manner in which a fixed abrasivepolishing tool containing an agent (water-absorbing resin) operates. Asshown in FIG. 14A, the fixed abrasive polishing tool has abrasiveparticles 301 and agent particles 302 which are fixed in place by abinder resin 303. The abrasive particles 301 have pores which areomitted from illustration as the pores have no definite shapes. Theagent particles 302 are made of a water-absorbing resin which can swellby absorbing water. As shown in FIG. 14B, when the fixed abrasivepolishing tool polishes a semiconductor wafer W, since a cooling mediumof water exists between the polishing surface of the fixed abrasive andthe semiconductor wafer W, the agent particles 302 absorb the water andare changed into swollen particles 302 a. As shown in FIG. 14C, when theabrasive particles 301 are brought into contact with the swollenparticles 302 a, the swollen particles 302 a resiliently bear theabrasive particles 301, thus resiliently polishing the semiconductorwafer W. FIG. 14D shows an agent particle 302 before it swells, and anagent particle 302 a after it has swollen by absorbing water. As shownin FIG. 14E, an agent particle 302 may be coated with a water-resistantcoating 302 c on its surface. The water-resistant coating 302 c may bemade of wax, but should preferably be made of Teflon (registeredtrademark), an acrylic resin, or other polymeric material.

[0123] Although certain preferred embodiments of the present inventionhave been shown and described in detail, it should be understood thatvarious changes and modifications may be made therein without departingfrom the scope of the appended claims.

What is claimed is:
 1. A polishing method for polishing a workpiece, comprising: pressing a workpiece against a polishing surface of a polishing tool containing a resin to bring the workpiece into sliding contact with said polishing tool, thereby polishing the workpiece with abrasive particles; wherein at least a part of said polishing tool is kept at a temperature equal to or lower than a glass transition temperature of said polishing tool.
 2. A method according to claim 1, wherein said polishing surface of said polishing tool is kept at said temperature equal to or lower than the glass transition temperature of said polishing tool.
 3. A method according to claim 1, wherein a table or a base plate on which said polishing tool is mounted is cooled to cool said polishing tool or regulate the temperature of said polishing tool to said temperature equal to or lower than the glass transition temperature of said polishing tool.
 4. A method according to claim 1, wherein a polishing liquid having a temperature equal to or lower than the glass transition temperature of said polishing tool is supplied to said polishing surface while the workpiece is being polished.
 5. A method according to claim 4, wherein said polishing liquid comprises cold water or a chemical liquid.
 6. A method according to claim 1, wherein a dressing liquid having a temperature equal to or lower than the glass transition temperature of said polishing tool is supplied to said polishing surface while said polishing surface is being dressed.
 7. A method according to claim 1, wherein a surface of the workpiece being polished is cooled to cool the surface of the workpiece or to regulate the temperature of the surface of the workpiece, thereby cooling said polishing tool or regulating the temperature of said polishing tool to said temperature equal to or lower than the glass transition temperature of said polishing tool.
 8. A method according to claim 1, further comprising: holding a processing assistance member in contact with said polishing surface; and cooling said processing assistance member or regulating the temperature of said processing assistance member to keep said polishing tool at said temperature equal to or lower than the glass transition temperature of said polishing tool.
 9. A method according to claim 8, wherein said processing assistance member comprises a dresser for dressing said polishing tool or a member attached to said dresser, said dresser or said member being held in contact with said polishing tool.
 10. A method according to claim 8, wherein said processing assistance member is operable independently of said dresser and a holder for holding the workpiece, and said processing assistance member is held in contact with said polishing tool.
 11. A method according to claim 8, wherein said processing assistance member is attached to a holder for holding the workpiece and held in contact with said polishing tool.
 12. A polishing method for polishing a workpiece, comprising: pressing a workpiece against a polishing surface of a polishing tool containing a resin to bring the workpiece into sliding contact with said polishing tool, thereby polishing the workpiece with abrasive particles; wherein a processing circumstance is kept at a temperature equal to or lower than a glass transition temperature of said polishing tool.
 13. A polishing apparatus for polishing a workpiece, comprising: a polishing tool containing a resin; a holder for holding and pressing a workpiece against said polishing tool to bring the workpiece into sliding contact with said polishing tool, thereby polishing the workpiece with abrasive particles; a temperature regulating device for keeping said polishing tool at a temperature equal to or lower than a glass transition temperature of said polishing tool.
 14. An apparatus according to claim 13, wherein said temperature regulating device cools a table or a base plate on which said polishing tool is mounted to cool said polishing tool or regulate the temperature of said polishing tool to said temperature equal to or lower than the glass transition temperature of said polishing tool.
 15. An apparatus according to claim 13, wherein a polishing liquid having a temperature equal to or lower than the glass transition temperature of said polishing tool is supplied to said polishing surface while the workpiece is being polished.
 16. An apparatus according to claim 15, wherein said polishing liquid comprises cold water or a chemical liquid.
 17. An apparatus according to claim 13, wherein a surface of the workpiece being polished is cooled to cool the surface of the workpiece or to regulate the temperature of the surface of the workpiece, thereby cooling said polishing tool or regulating the temperature of said polishing tool to said temperature equal to or lower than the glass transition temperature of said polishing tool.
 18. An apparatus according to claim 13, further comprising: a processing assistance member which is brought in contact with said polishing surface; and a temperature regulating device for cooling said processing assistance member or regulating the temperature of said temperature regulating device to keep said polishing tool at said temperature equal to or lower than the glass transition temperature of said polishing tool.
 19. An apparatus according to claim 18, wherein said processing assistance member comprises a dresser for dressing said polishing tool or a member attached to said dresser, said dresser or said member being held in contact with said polishing tool.
 20. An apparatus according to claim 18, wherein said processing assistance member is operable independently of said dresser and a holder for holding the workpiece, and said processing assistance member is held in contact with said polishing tool.
 21. An apparatus according to claim 18, wherein said processing assistance member is attached to a holder for holding the workpiece and held in contact with said polishing tool.
 22. A method of manufacturing a polishing tool, comprising: drying a mixed liquid including a resin and chemical agents to form a dried solid material; and compressing and forming said dried solid material with heat into a polishing tool; wherein said drying temperature is lower than the temperature of said compressing and forming.
 23. A method according to claim 22, wherein said mixed liquid includes abrasive particles.
 24. A method of manufacturing a polishing tool, comprising: drying a mixed liquid including a resin and chemical agents to form a dried solid material; and compressing and forming said dried solid material with heat into a polishing tool; wherein the temperature of said compressing and forming is higher than a glass transition temperature of said resin or a dissolution temperature of said resin.
 25. A method according to claim 24, wherein said mixed liquid includes abrasive particles.
 26. A method of manufacturing a polishing tool, comprising: drying a mixed liquid including a resin and chemical agents to form a dried solid material; and compressing and forming said dried solid material with heat into a polishing tool; wherein a resin solvent is added to said mixed liquid.
 27. A method according to claim 26, wherein said mixed liquid includes abrasive particles.
 28. A method of manufacturing a polishing tool, comprising: drying a mixed liquid including a resin and chemical agents to form a dried solid material; and compressing and forming said dried solid material with heat into a polishing tool; wherein an organic solvent or a foaming agent is added to said dried solid material.
 29. A method according to claim 28, wherein said mixed liquid includes abrasive particles. 